have a roving eye idiom  old-fashioned humorous      
 色迷迷;总找机会寻花问柳
If you say that someone has a roving eye, you mean that they are always sexually interested in people other than their partner.
  By his own admission he had a roving eye and was easily infatuated. 
Although he's going out with one of the world's most beautiful women, the actor still has a roving eye.